A recent study challenges the depiction of predatory dinosaurs like Tyrannosaurus rex with exposed teeth, suggesting they had scaly, lizard-like lips instead. By examining tooth structure, wear patterns, and jaw morphology of reptile groups, researchers concluded that theropod mouth anatomy resembles lizards more than crocodiles. The findings imply that many popular dinosaur depictions, including the iconic Jurassic Park T. rex, are incorrect. This research provides valuable insights into the appearance, feeding habits, dental health, and evolutionary patterns of dinosaurs and other extinct species.
A new study suggests that predatory dinosaurs, such as Tyrannosaurus rex, did not have permanently exposed teeth as depicted in films such as Jurassic Park, but instead had scaly, lizard-like lips covering and sealing their mouths.
Researchers and artists have debated whether theropod dinosaurs, the group of two-legged dinosaurs that includes carnivores and top predators like T. rex and Velociraptor, as well as birds, had lipless mouths where perpetually visible upper teeth hung over their lower jaws, similar to the mouth of a crocodile.
However, an international team of researchers challenge some of the best-known depictions, and say these dinosaurs had lips similar to those of lizards and their relative, the tuatara – a rare reptile found only in New Zealand, which are the last survivors of an order of reptiles that thrived in the age of the dinosaurs.
In the most detailed study of this issue yet, the researchers examined the tooth structure, wear patterns and jaw morphology of lipped and lipless reptile groups and found that theropod mouth anatomy and functionality resembles that of lizards more than crocodiles. This implies lizard-like oral tissues, including scaly lips covering their teeth.
These lips were probably not muscular, like they are in mammals. Most reptile lips cover their teeth but cannot be moved independently – they cannot be curled back into a snarl, or make other sorts of movements we associate with lips in humans or other mammals.
Study co-author Derek Larson, Collections Manager and Researcher in Palaeontology at the Royal BC Museum in Canada, said: “Palaeontologists often like to compare extinct animals to their closest living relatives, but in the case of dinosaurs, their closest relatives have been evolutionarily distinct for hundreds of millions of years and today are incredibly specialised.
“It’s quite remarkable how similar theropod teeth are to monitor lizards. From the smallest dwarf monitor to the Komodo dragon, the teeth function in much the same way. So, monitors can be compared quite favourably with extinct animals like theropod dinosaurs based on this similarity of function, even though they are not closely related.”
Co-author Dr Mark Witton from the University of Portsmouth said: “Dinosaur artists have gone back and forth on lips since we started restoring dinosaurs during the 19th century, but lipless dinosaurs became more prominent in the 1980s and 1990s. They were then deeply rooted in popular culture through films and documentaries — Jurassic Park and its sequels, Walking with Dinosaurs and so on.
“Curiously, there was never a dedicated study or discovery instigating this change and, to a large extent, it probably reflected preference for a new, ferocious-looking aesthetic rather than a shift in scientific thinking. We’re upending this popular depiction by covering their teeth with lizard-like lips. This means a lot of our favourite dinosaur depictions are incorrect, including the iconic Jurassic Park T. rex.”
The results, published in the journal Science, found that tooth wear in lipless animals was markedly different from that seen in carnivorous dinosaurs and that dinosaur teeth were no larger, relative to skull size, than those of modern lizards, implying they were not too big to cover with lips.
Also, the distribution of small holes around the jaws, which supply nerves and blood to the gums and tissues around the mouth, were more lizard-like in dinosaurs than crocodile-like. Furthermore, modelling mouth closure of lipless theropod jaws showed that the lower jaw either had to crush jaw-supporting bones or disarticulate the jaw joint to seal the mouth.
“As any dentist will tell you, saliva is important for maintaining the health of your teeth. Teeth that are not covered by lips risk drying out and can be subject to more damage during feeding or fighting, as we see in crocodiles, but not in dinosaurs,” said co-author Kirstin Brink, Assistant Professor of Palaeontology at the University of Manitoba.
She added: “Dinosaur teeth have very thin enamel and mammal teeth have thick enamel (with some exceptions). Crocodile enamel is a bit thicker than dinosaur enamel, but not as thick as mammalian enamel. There are some mammal groups that do have exposed enamel, but their enamel is modified to withstand exposure.”
Thomas Cullen, Assistant Professor of Paleobiology at Auburn University and study lead author, said: “Although it’s been argued in the past that the teeth of predatory dinosaurs might be too big to be covered by lips, our study shows that, in actuality, their teeth were not atypically large. Even the giant teeth of tyrannosaurs are proportionally similar in size to those of living predatory lizards when compared for skull size, rejecting the idea that their teeth were too big to cover with lips.”
The results provide new insights into how we reconstruct the soft tissues and appearance of dinosaurs and other extinct species. This can give crucial information on how they fed, how they maintained their dental health, and the broader patterns of their evolution and ecology.
Dr Witton said: “Some take the view that we’re clueless about the appearance of dinosaurs beyond basic features like the number of fingers and toes. But our study, and others like it, show that we have an increasingly good handle on many aspects of dinosaur appearance. Far from being clueless, we’re now at a point where we can say ‘oh, that doesn’t have lips? Or a certain type of scale or feather?’ Then that’s as realistic a depiction of that species as a tiger without stripes.”
The researchers point out that their study doesn’t say that no extinct animals had exposed teeth — some, like sabre-toothed carnivorous mammals, or marine reptiles and flying reptiles with extremely long, interlocking teeth, almost certainly did.
For more on this research, see Deadly Teeth of T. rex Were Hidden Behind Scaly Lips.
Reference: “Theropod dinosaur facial reconstruction and the importance of soft tissues in paleobiology” by Thomas M. Cullen, Derek W. Larson, Mark P. Witton, Diane Scott, Tea Maho, Kirstin S. Brink, David C. Evans and Robert Reisz, 30 March 2023, Science.
Dinosaurs had lips. Wonderful. Thank you science. Now, how’s that cure for cancer coming along?
I see problem the use of velociraptor struthiomimus as dinosaur clearly are flightless bird and the name archosaur and nonavian name and not support spinosauridae as a mesoeucrocodylia the spinosauridae gator does not have lip the living spinosauridae dinosaur the tetanuran dinosaur nile crocodile the champion dinosaur does not have lip .the monitor does have big teeth like theropod tetanuran and it’s ziphodont but story forgot to say ziphodont teeth is found in fossil mesoeucrocodylia I doubt any won will say that for fossil ziphodont mesoeucrocodylia allso one of dwarf caiman a well known land crocodilian close to having ziphodont teeth only different it lack serration it’s alligator only in crocodile it is serrated the teeth in dwarf caiman is curve like tetanuran dinosaur .and the reason why sensory foramen in crocodile are not like t.rex .t.rex is a land animal that lack kink snout like most predator tetanuran or lack wave snout found in eusuchian mesoeucrocodylia they have better bite force .all tetanuran and ceratosaurus have those sensory foramen they do not use foramen you see on the skull they use one goes to the brain that why t.rex and the gator have the most sensoritive face out any animal and velociraptor and struthiomimus do not have these face sensory because they are bird they are not dinosaur.on spinosaurus 7 foramen of paroccipital processes like gator it is vagus nerves like the gator the link braincase of almadasuchus.the other foramen very mesoeucrocodylia feature cranioquadrate passage the foramen is bigger only can identified in mesoeucrocodylia because protosuchus does not have it so no identified but protosuchus do have vagus foramen but likely do not have basioccipital fuse with basisphenoid because they have bad hearing like t.rex not like champion dinosaur good hearing the gator.spinosaurus allso has gator 7 foramen the link new information on the skull of the enigmatic academi edu.baryonyx 7 foramen on my old report surrey.five back leg toe hesperosuchus and lizard lack most sensoritive face out any animal because they are not mesoeucrocodylia .
I forgot macelognathus cranioquadrate passage they are same line as almadasuchus they are clearly mesoeucrocodylia with a fuse frontals macelognathus was a juvenile so it’s not fuse .the link the detailed braincase of the macelognathus .and clearly spinosauridae is a mesoeucrocodylia they have same feature found in armor dinosaur I did not find it in spinosauridae some thing that easy is hard to find why.? Of course I find that feature in gator and armor dinosaur which show it could be done in the gator and dinosaur because they are link all are dinosaur that feature I can not say mite tip off people and I will never find it but I still have armor dinosaur ?
Monitor lizard teeth one in this story looks like t.rex Nile crocodile gator teeth it’s a predator teeth a space teeth I thought it only found in dinosaur these close teeth found in most theropod baryonyx lizard is primitive .wear t.rex and gator are simular and modern crocodilian skull very different from rest of dinosaur only dinosaur simular is t.rex .spinosauridae is a true mesoeucrocodylia .t.rex even in thecodont t.rex only simular to gator .protosuchus rauisuchus all eat simular to birds like most tetanuran dinosaur up and down t.rex and gator are twisted predator jaw predator only in mesoeucrocodylia there is a death roll system most tetanuran dinosaur serrated teeth it’s not for crushing bone it’s to rip flesh off big wound it’s a good system that’s why mesoeucrocodylia brought back ziphodont teeth many times only tetanuran dinosaur design to crush bone is t.rex that why there feature is simular to modern crocodilian like strong bite force muscle mandibularis this feature is unique to modern crocodilian a eusuchian mesoeucrocodylia feature a advance mesoeucrocodylia feature.and gator lower jaw is simular to mammal all bone are fuse in gator the mammal lower jaw only one bone a solid jaw a predator feature t.rex lower jaw is not fuse like primitive reptile it is advance thou there is story about that i think it was coronoid bone clearly teeth are going to be different and wear .I saw early land gator type mesoeucrocodylia story I think it is about teeth they say its unique predator feature only found in t.rex spinosauridae and modern crocodilian and most modern crocodilian are semi aquatic predator . On the surrey report they say double foramen the cranioquadrate passage